Enamel composition



Patented June 26, 1945 ENAMEL COMPOSITION John w. Gan-non, Cleveland, 01110, assig'nor to General Electric Company, a corporation of New York No Drawing. Application May 20, 1941,

} Serial No. 394,361

2 Claims.

My invention relates in general to enamel compositions and more particularly to non-lead enamel compositions. The enamel comprising my invention is especially adapted for application as a coating to glass electric lamp bulbs and it may be applied to the exterior surfaces of ordinary lamp bulbs or to the interior or exterior surfaces of glass tubes.

It is an object of the present inventiomto provide an enamel having a desirable, comparative-- ly low, coefllcient of expansion. A' further object is to provide, an enamel having a comparatively low softening point of not more than about 1200" F.

A still further object is to provide an enamel having high stability, 1. e., resistance to chemical attack by weather and cleaning agents.

A still further object is to produce an enamel which is opalescent but not transparent without the aid of mill additions of opacifying materials.

Further objects and advantages will appear from the following description.

It is well known that certain enamel making materials tend, when incorporated in the enamel, to produce one orv more desirable results but in so doing many of them also work against other desirable results. It cannot be predicted in advance how a variation of the relative proportions of the different ingredients will affect certain of the features referred to in the objects of this invenion. The present invention therefore contemplates the selection of certain known nonlead enamel making materials in such relative proportions as will produce an enamel having the desired properties referred to above.

One of the features of the enamel compositions comprising my invention is that there is present an amount of zinc oxide which is preferably at least as great as that of any other single major constituent. Another feature is the production of a low melting zinc borosilicate composition containing an opacifying content of zinc oxide. Another feature is a high percentage of zinc oxide, preferably greater than about 28 per cent, which tends to produce high stability. An-

other feature is that the zinc borosilicate enamel has a low coeflicient of expansion of about at 92 0.. 02 at 185 0. and 07.5 at 300 0.

The objects of my invention are attained in and having a composition as follows:

Rammh Frit Percent 6 200.0 510.----- 200.0 25. 10.0 A1201.... .7 3&0 000..... 35.0 4. 210.0 ZnO 270.0 20. 80.0 Ba0 47.0 0. 300.0 13,05"--. 186.0 23. 15.0 AS203 5.0 57.5 o 30.2 5. 07.5 N8:Q 30.0 5.

It isimportant that the barium oxide be introduced as barium nitrate. I also prefer to use crystalline boric acid rather than the granular form because it melts more easily.

In preparing the enamel, the raw materials are first mixed together and placed in contain- .ers free from all contamination. The mixture is then placed in a. smelting furnace, either of the continuous or pot type, at a temperature of approximately 900 C. The melted batch is then discharged into water to break it up, and is then placed in metal trays to dry.

The followingare examples of three additional enamel compositions which fall within the scope of this invention:

Frit Per cent Frit Percent Frit Percent .0 27. a2 2;: as 02 30.0 4.5 35.0 4.1 05.0 4. 220.0 28.2 no.0 27.2 220.0 27. 40.0 0.0 47.0 5.0 47.0 0. 175.0 22.5 175.0 20.7 178.0 22. 5.0 .0 5.3 gg 0. a I i 10 015 3017 a 'l'heennmelturtherconteinl-theoxideeotnluminum,cadmiumendbu-iuminemtflmmtot about 10to15pereent,whileaihlioxideeere presentinannmount of about 8-151: cent.

whetIclaimunewenddesil-etoaecureby Letters Patent of the United States is:

1. A zinoborosilicete ennmel composition oom- 'prisinzboricouidemdaiiiceinmammmtequal to approximately 50 per cent by weight of the total composition, and zinc oxide in on amount at least about equal by yeightio that of any other sinzle constituent, the said boric oxide, silica and zinc oxide constituting. approximately 75 per cent by weilht o! the total com osition, the composition further containing the oxide; 01' aluminum. cadmium and berium in a total emountotepm'oximnielv lotolineremtmd approximate 8 to}! per cent at nib-Ii oxides.

2.Azinoborosilicateennmeihavinw0ximeteiy the toilowinz composition by weight:

7 Per cent 810: 25-28 A110: 1- 4. CdO 4- 5 2110 26-30 8:0 5- 7 B10: 20-24 A310: 0.6 K10 4 7 8:10 4- 7 JOHN W. GARRIBON. 

